In 1999, the California Air Resources Board (CARB) initiated its Neighborhood Assessment Program (NAP) to develop tools to assess the cumulative impacts of air pollutant emissions on neighborhood and local scales. 

CARB sponsored UCR to develop dispersion models and collect the associated data sets that can be used to estimate the impact of urban sources at source-receptor distances of tens of meters to several kilometers.  Two experiments, CE-CERT experiment and Barrio Logan experiment, were conducted for this project.

To estimate the impact of urban sources at source-receptor distances of meters, a tracer experiment was designed and conducted at a parking lot of the College of Engineering’s Center for Environmental Research and Technology (CE-CERT).

Experimental Setup

SF₆ line source and sampling sites

Variation of observed and estimated concentrations as a function of deviation of wind direction from source-receptor line

The model evaluation clearly indicates the importance of including the randomizing effect of buildings on wind directions

Air Quality Model with Meandering (AQMM) predicts better
results than those from other regulatory models by
accounting for wind direction meandering near the source

The model for source-receptor distances of the order of kilometers was evaluated with data derived from two tracer experiments conducted during August and December of 2001 at Barrio Logan, San Diego. 

Observed turbulent intensities vary by less
than 20% in the vertical in the boundary layer

Model performance when initial
spreads are taken to be zero

Better model performance when initial
horizontal spread is taken to be 50m

It's necessary to account for initial plume
 spread caused by building effects to explain concentrations on the 200m and 500m arcs.

Model performance based on turbulent intensities
averaged over the entire field study is almost as well as the
 model performance using experiment specific meteorology

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